Infrared radiation process for a high contrast in the natural grain of a naturally pale wood

Abstract

A process brings out a high contrast in natural grain of a naturally pale wood via infrared irradiation having a wavelength which is as long as possible. This infrared radiation can come from a conventional infrared emitter or, more preferably, from a carbon dioxide laser. Due to the contact-free heating near the surface which is effective in a stagnant ambient atmosphere, the new wood part of the grain is browned, while the harder old wood part remains essentially unbrowned. This causes the natural grain of the wood to stand out in contrast. Due to the contact-free and turbulence-free mode of operation of the heating, the grain pattern produced is uniform. Any scratches or chatter marks in the wood are simply covered over and remain invisible.

What is claimed: 
     
       1. A process for bringing out a contrast in a grain pattern of a wood component having portions of different age which have insufficient original contrast relative to each other and consisting essentially of one of a solid piece of wood, a veneered component and a veneer sheet, comprising the step of applying heat to a visible face of the component near the surface thereof for a period of time sufficient only to cover the entire surface of the compound with uniform heat intensity for bringing out the contrast, in a contact-free manner, through infrared radiation in a stagnant ambient atmosphere. 
     
     
       2. The process according to claim 1, wherein a specific energy quantity of 15 to 60 Ws/cm 2  is used in the heat application step. 
     
     
       3. The process according to claim 1, wherein the heat application step per unit of the surface covered occurs in a time span of from half a second to two seconds. 
     
     
       4. The process according to claim 3, wherein a specific energy quantity of 15 to 60 Ws/cm 2  is used in the heat application step. 
     
     
       5. The process according to claim 1 wherein the heat application step is carried out at least partially by an infrared emitter. 
     
     
       6. The process according to claim 5, wherein a specific energy quantity of 15 to 60 Ws/cm 2  is used in the heat application step. 
     
     
       7. The process according to claim 5, wherein the heat application step per surface element is limited to a time span of from half a second to two seconds. 
     
     
       8. The process according to claim 1, wherein the infrared radiation contains mainly wavelengths of over 2 μm. 
     
     
       9. The process according to claim 8, wherein a specific energy quantity of 15 to 60 Ws/cm 2  is used in the heat application step. 
     
     
       10. The process according to claim 9, wherein the heat application step per surface element is limited to a time span of from half a second to two seconds. 
     
     
       11. The process according to claim 10, wherein the heat application step is carried out at least partially by an infrared emitter. 
     
     
       12. The process according to claim 1, wherein the heat application step is carried out by a heat source comprising a carbon dioxide laser. 
     
     
       13. The process according to claim 12, wherein the diverging part of a focused laser beam from the laser is applied to the surface of the component. 
     
     
       14. The process according to claim 13, wherein a specific energy quantity of 15 to 60 Ws/cm 2  is used in the heat application step. 
     
     
       15. The process according to claim 14, wherein the heat source includes an infrared emitter. 
     
     
       16. The process according to claim 1, wherein the heat application step takes place with a relative shift between the component and a heat source providing an infrared radiation beam at a constant distance there between, as measured in the direction of the beam. 
     
     
       17. The process according to claim 16, wherein the relative shift takes place at speed of about 3 to 10 m/min. 
     
     
       18. The process according to claim 1, wherein the grain contrasted through the infrared radiation is fixed by application of a clear varnish for protection from dirt or smudging during further processing. 
     
     
       19. The process according to claim 1, wherein the component is ash wood. 
     
     
       20. The process according to claim 1, wherein the component is moved in a conveyance direction relative to a source of the infrared radiation, with the source providing a focal spot which is moved at high frequency in a direction transverse to the conveyance direction. 
     
     
       21. The process according to claim 1, wherein a source of the infrared radiation is oscillated in an arcuate path, and the component is curved to conform to the arcuate path of the source. 
     
     
       22. The process according to claim 1, wherein a source of the infrared radiation provides a beam which is oscillated relative to a direction of conveyance of the component, and at least one of a speed of the oscillation and an output of the beam is varied to maintain a desired beam intensity. 
     
     
       23. The process according to claim 1, where a source of the infrared radiation is a laser beam which strikes the component with a diverging portion of the beam to provide a focal spot of sufficient size to treat a large area of the component.